Only about two dozen bats were alive in the Durham mine site in eastern Pennsylvania's Bucks County when state Game Commission biologist Greg Turner visited it in late February for the first time in two years, Phillyburbs.com reported Sunday. Half of the survivors showed clear signs of infection, he told the news website.
The county's bat population has been decimated by white nose syndrome, a disease that has been wiping out bat colonies across the Northeast United States the past four years.
The disease causes bats to lose the body fat they need to survive hibernation.
"The important thing is that we're still seeing declines at that site," he said.
The drop in the Dunham cave's bat population was first noticed in January 2011, and biologists determined it was too late to save them. By March 2011, just 180 remained, and half of those had the telltale white fungus around their muzzles, leaving the scientists with little hope in the colony's ability to reproduce and survive.
Phillyburbs.com said the state biologists won't visit the gated, hillside mine for another two years.
Turner said federal scientists are in the process of determining if the six species of cave bats will be included in the endangered species list. He said 98 percent of Pennsylvania's cave-hibernating bats have died.
"Going to places where there used to be tens of thousand bats hibernating, and then going in and seeing only a few bats -- only a few stragglers left -- that's very difficult," he said.